NERVOUS SYSTEM, SENSES, AND SENSE ORGANS 183 



external orifice. In some of the Eels {Apodes) the anterior nostril 

 is situated on the upper lip (labial position) and in many of 

 the Globe-fishes ( Tetrodontidae) there are no actual apertures but 

 a pair of solid nasal tentacles. 



Most of the oceanic Ceratioid Angler-fishes with line and 

 bait have small eyes and normal nostrils (Figs. 31, 91B), but 

 certain forms [Lipactis, Rhynchoceratias) have the lure altogether 

 wanting, and the eyes and nostrils are more or less enlarged, 



Fig. 72. NOSTRILS AND NASAL ORGANS. 



A. Sea Lamprey {Petrotnyzon marinus),x^ ; a'. Upper view of head of same ; 



B. Head of Herring (Clupea harengus), X -^ ; b'. Front part of head dissected to 

 show nasal organ. (After Derscheid) ; c. Aceratias macrorhintis, x about 2 ; 



n., nostril. 



perhaps indicating that they seek their food by smell and sight 

 {cf. p. 315). In the genus Aceratias (Fig. 720) the lure is again 

 absent, the eyes are directed forwards, the snout is shortened in 

 relation to the stereoscopic vision (as in man), and the olfactory 

 organs are relatively enormous. They are, however, developed on 

 a somewhat diflferent plan, one nostril being at the end of a tube. 

 There can be little doubt that the sense of smell in fishes is 

 relatively acute, as has been proved by numerous experiments. 

 The large nasal organs of Sharks are said to enable them to 



